In recent years, our society has developed an increased interest in health and physical fitness. A popular method of improving physical fitness and maintaining better health involves weight lifting. Health spas have blossomed around the country, offering a wide range of weight lifting equipment.
Generally, different types of weight lifting machines have been developed to exercise particular muscle groups. For example, there are different weight lifting machines available to exercise the biceps, triceps, deltoids, latissimus dorsi, quadriceps, and calf muscles, to name a few.
Most conventional weight lifting machines available today function by a lever or pulley mechanism or some combination of both of these. Generally, a stack of weights is placed at a fixed spot on a lever or at the end of a pulley cable. Each weight in the stack has an orifice for the insertion of a metal pin. Insertion of the pin in a particular orifice results in all the weights above the pin serving as the resisting force when an exercise is performed. An appropriate handle is attached at the other end of the lever or pulley, depending on the exercise that is to be performed. The amount of weight can be varied in discrete increments by changing the position of the metal pin. In some types of pulley machines, a gear mechanism of a particular shape, such as a kidney shape, rests between the weights and the handle to vary the amount of input required to lift a given amount of weight as a function of the distance that the weights have been lifted.
In order to achieve maximum results from weight lifting, whether it is desired to add muscle bulk or increase muscle definition, it is important that a particular muscle being exercised fail completely by the end of the exercise. Each muscle group is composed of various sub-muscle groups. When a person bench presses, for example, 200 pounds for a number of repetitions until he can no longer perform another repetition, only the weakest sub-muscle groups within the pectoralis (chest) muscle will have failed. In order to achieve failure of the remaining sub-muscle groups, the amount of weight being lifted would need to be decreased until further repetitions could be performed. Optimally, the effective weight should be continuously decreased until all of the sub-muscle groups have failed.
In order to decrease the effective weight being lifted on conventional equipment, the exerciser must stop the exercise, get up from the machine, change the position of the pin, get back on the machine, and continue to exercise. By the time all this has taken place, the sub-muscle groups that failed have substantially recovered. Thus, when the exercise is resumed, these sub-muscle groups are once again being used, and the desired failure of the remaining sub-muscle groups will not occur. In addition, on conventional equipment, the effective weight may be reduced or increased only in discrete increments. These increments may be too large to isolate and cause failure of specific sub-muscle groups.
It would be extremely advantageous to have a weight lifting apparatus which allows the continuous variation of the effective weight, the controls for such variation being accessible to the exerciser while in the exercise position, and such variation being possible while the exerciser is performing an exercise stroke. The present invention satisfies these needs and provides other related advantages.